1. Field of the Invention
The present invention relates to electrically powered aquatic vehicles of the type particularly suited for pulling swimmers and divers to underwater depths.
2. Description of the Prior Art
As an electromechanical propulsion system, vehicles or vessels of the present type are conceptively simple as comprising only a small body shell for housing a d.c. motor, a direct drive propeller, a battery for energizing the motor, a motor control switch and a user's grasp handle. However, due to the hostile underwater operating environment, conditions for safety and reliability quickly complicate the design choices.
Wet cell lead/acid batteries provide the least expansive and conveniently rechargeable energy source but are simultaneously the source of combustible hydrogen gas. If generated, the gas must be purged from the system to avoid the risk of explosion.
Brush/commutator d.c. motors provide the most economical torque and operational efficiency for the service but also offer an exposed arc ignition source for any combustible gas mixture present.
Buoyancy demands for such a vehicle quickly change by the user's needs, concerns, safety and whim. Preferably, the user would choose to rapidly select between reversible options of positive, negative or neutral buoyancy. There are times when the user would prefer that his personal vehicle simply remain suspended when released.
Other times, he would have the vehicle rise to the surface when released. A negatively buoyant vehicle will descend by gravity to the first support surface.
Most such vehicles are steered by physical pointing which requires some form of twisting or torque couple, consequently, placement of the manual handgrip position relative to buoyancy and weight distribution is critical. Instability and excessive coupling lead to user fatigue.
Finally, when a prior art vehicle is out of the water with charge remaining in the battery, the propeller becomes a hazardous source of personal injury.
It is, therefore, an object of the present invention to teach the construction of a personal underwater tow vehicle that is substantially free of gas explosion hazards.
Another object of the present invention is to provide a personal underwater tow vehicle that will not leak battery acid.
Another object of the present invention is to provide a personal underwater tow vehicle having a continuously reported state of battery charge.
Another object of the present invention is to provide a personal underwater tow vehicle that is easily and comfortably steered.
Another object of the present invention is to provide a personal underwater tow vehicle in which the propeller power circuit is rendered inoperative when the vehicle is out of water.
A still further object of the present invention is to facilitate immediate and in-use buoyancy adjustments.